Effects of Actin-Myosin Kinetics on the Calcium Sensitivity of Regulated Thin Filaments

Sich, Nicholas M.; O’Donnell, Timothy J.; Coulter, Sarah A.; John, Olivia A.; Carter, Michael S.; Cremo, Christine R.; Baker, Josh E.

doi:10.1074/jbc.m110.142232

Cited by 16 publications

(24 citation statements)

References 52 publications

(64 reference statements)

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“…This has been supported by a number of biochemical studies, including work showing the Ca 2+ sensitivity of in vitro motility velocities [62], 64. One question, though, has been whether cardiomyopathy-causing troponin mutations can alter the maximal Ca 2+ -activated myosin ADP release cross-bridge kinetics.…”

Section: Discussionmentioning

confidence: 96%

Effects of Troponin T Cardiomyopathy Mutations on the Calcium Sensitivity of the Regulated Thin Filament and the Actomyosin Cross-Bridge Kinetics of Human β-Cardiac Myosin

et al. 2013

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Hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) lead to significant cardiovascular morbidity and mortality worldwide. Mutations in the genes encoding the sarcomere, the force-generating unit in the cardiomyocyte, cause familial forms of both HCM and DCM. This study examines two HCM-causing (I79N, E163K) and two DCM-causing (R141W, R173W) mutations in the troponin T subunit of the troponin complex using human β-cardiac myosin. Unlike earlier reports using various myosin constructs, we found that none of these mutations affect the maximal sliding velocities or maximal Ca2+-activated ADP release rates involving the thin filament human β-cardiac myosin complex. Changes in Ca2+ sensitivity using the human myosin isoform do, however, mimic changes seen previously with non-human myosin isoforms. Transient kinetic measurements show that these mutations alter the kinetics of Ca2+ induced conformational changes in the regulatory thin filament proteins. These changes in calcium sensitivity are independent of active, cycling human β-cardiac myosin.

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Section: Discussionmentioning

confidence: 96%

Effects of Troponin T Cardiomyopathy Mutations on the Calcium Sensitivity of the Regulated Thin Filament and the Actomyosin Cross-Bridge Kinetics of Human β-Cardiac Myosin

et al. 2013

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“…• C is only ∼50% of maximum (Jacobs et al, 2011), and otherwise depends on intracellular Ca 2+levels, saturating at ∼10 µM, at least in thin filaments (Sich et al, 2010). In view of the field-strength dependent up-regulation of TRPM7, another intriguing possibility would also be that TRPM7-upregulation might actually constitute a homeostatic mechanism to raise Ca 2+ flux to limit migration speed-obviously, this hypothesis also awaits testing in further experiments.…”

Section: Discussionmentioning

confidence: 97%

Human Osteoblast Migration in DC Electrical Fields Depends on Store Operated Ca2+-Release and Is Correlated to Upregulation of Stretch-Activated TRPM7 Channels

Rohde

Ziebart

Kirschstein

et al. 2019

Front. Bioeng. Biotechnol.

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Fracture healing and bone regeneration, particularly in the elderly, remains a challenge. There is an ongoing search for methods to activate osteoblasts, and the application of electrical fields is an attractive approach in this context. Although it is known that such electromagnetic fields lead to osteoblast migration and foster mesenchymal osteogenic differentiation, so far the mechanisms of osteoblast activation remain unclear. Possible mechanisms could rely on changes in Ca 2+ -influx via ion channels, as these are known to modulate osteoblast activity, e.g., via voltage-sensitive, stretch-sensitive, transient-receptor-potential (TRP) channels, or store-operated release. In the present in vitro study, we explored whether electrical fields are able to modulate the expression of voltage-sensitive calcium channels as well as TRP channels in primary human osteoblast cell lines. We show migration speed is significantly increased in stimulated osteoblasts (6.4 ± 2.1 µm/h stimulated, 3.6 ± 1.1 µm/h control), and directed toward the anode. However, within a range of 154-445 V/m, field strength did not correlate with migration velocity. Neither was there a correlation between electric field and voltage-gated calcium channel (Ca v 3.2 and Ca v 1.4) expression. However, the expression of TRPM7 significantly correlated positively to electric field strength. TRPM7 channel blockade using NS8593, in turn, did not significantly alter migration speed, nor did blockade of Ca v 3.2 and Ca v 1.4 channels using Ni + or verapamil, respectively, while a general Ca 2+ -influx block using Mg 2+ accelerated migration. Stimulating store-operated Ca 2+ -release significantly reduced migration speed, while blocking IP3 had only a minor effect (at low and high concentrations of 2-APB, respectively). We conclude that (i) store operated channels negatively modulate migration speed and that (ii) the upregulation of TRPM7 might constitute a compensatory mechanism-which might explain how increasing expression levels at increasing field strengths result in constant migration speeds.

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“…Kinetic studies suggest it is the rate of Ca 2+ binding to TnC that is increased by HCM mutations [34]. It is remarkable that two HCM mutations in different regions of myosin light chain 2 and two β-myosin heavy chain mutations also increase myofibrillar Ca 2+ -sensitivity [30,35], indicating that small changes in myosin-actin interactions exert allosteric effects upon the thin filament switch to change Ca 2+ -sensitivity [36].…”

Section: Can a Single Sarcomeric Abnormality Cause All Cases Of Hcm?mentioning

confidence: 98%

How Do Mutations in Contractile Proteins Cause the Primary Familial Cardiomyopathies?

Marston

2011

J. of Cardiovasc. Trans. Res.

114

131

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In this article, the available evidence about the functional effects of the contractile protein mutations that cause hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) is assessed. The molecular mechanism of the contractile apparatus of cardiac muscle and its regulation by Ca(2+) and PKA phosphorylation have been extensively studied. Therefore, when a number of point mutations in the contractile protein genes were found to cause the well-defined phenotypes of HCM and DCM, it was expected that the diseases could be explained at the molecular level. However, the search for a distinctive molecular phenotype did not yield rapid results. Now that a substantial number of mutations that cause HCM or DCM have been investigated in physiologically relevant systems and with a range of experimental techniques, a pattern is emerging. In the case of HCM, the hypothesis that the major effect of mutations is to increase myofibrillar Ca(2+)-sensitivity seems to be well established, but the mechanisms by which an increase in myofibrillar Ca(2+)-sensitivity induces hypertrophy remain obscure. In contrast, DCM mutations are not correlated with a specific effect on Ca(2+)-sensitivity. It has recently been proposed that DCM mutations uncouple troponin I phosphorylation from Ca(2+)-sensitivity changes, albeit based on only a few mutations so far. A plausible link between uncoupling and DCM has been proposed via blunting of the response to α-adrenergic stimulation.

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Effects of Actin-Myosin Kinetics on the Calcium Sensitivity of Regulated Thin Filaments

Cited by 16 publications

References 52 publications

Effects of Troponin T Cardiomyopathy Mutations on the Calcium Sensitivity of the Regulated Thin Filament and the Actomyosin Cross-Bridge Kinetics of Human β-Cardiac Myosin

Effects of Troponin T Cardiomyopathy Mutations on the Calcium Sensitivity of the Regulated Thin Filament and the Actomyosin Cross-Bridge Kinetics of Human β-Cardiac Myosin

Human Osteoblast Migration in DC Electrical Fields Depends on Store Operated Ca2+-Release and Is Correlated to Upregulation of Stretch-Activated TRPM7 Channels

How Do Mutations in Contractile Proteins Cause the Primary Familial Cardiomyopathies?

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